Locating the sources of ultra-high energy cosmic rays (UHECRs) still remains a difficult puzzle for modern astrophysics. A major hurdle in the search for the sources is the fact that UHECRs are deflected by the Galactic magnetic field (GMF). Current knowledge of the GMF is limited, as most experimental measurements track line-of-sight–integrated quantities that are used to obtain best-fit parameters for global models including a large random component. The advent, however, of the Gaia era, with measurements of $\sim 10^9$ stellar parallaxes, in combination with upcoming large polarimetric surveys, such as PASIPHAE, will allow, for the first time, a 3D measurement of the GMF, which can then be used for a meaningful correction of the UHECR trajectories through the Galaxy.
In the present work, we examine how the effectiveness of such a correction depends on the uncertainty of magnetic field measurements. To that end, we simulate attempts to reconstruct the trajectory of the cosmic ray by using hypothetical measurements of the GMF, based on values received from two recently updated GMF models. To simulate the uncertainty of a 3D measurement, random errors to these values are introduced separately for the plane-of-the-sky (POS) magnitude, the line-of-sight (LOS) magnitude and the POS direction.
Our results show that an effective correction is in many cases achievable without need for extreme measurement precision. The effectiveness of the correction is heavily dependent on the particle rigidity and arrival direction and can vary significantly depending on the GMF model used.
G. Magkos and V. Pavlidou
Tue, 13 Feb 18
Comments: 20 pages, 6 figures, comments welcome